Many fluid processing techniques entail the centrifugation of large volumes of fluids. To minimize processing times, these techniques often require the use of relatively high flow rates. Increasingly, such techniques are being used in the medical field.
For example, in the areas of biotechnology and adoptive immunotherapy, it is necessary to process relatively large volumes of cultured cellular products by centrifugation. Through centrifugation, cultured cells are separated from the supernatant for the purpose of replacing/exchanging the culture medium; or for providing a cell-free supernatant for the subsequent collection of antibodies or for subsequent use as an additive to culture medium; or for the collection of concentrated cellular product.
In the area of adoptive immunotherapy, it has been possible to process between 10 to 50 liters of cultured LAK (Limphokine Activated Killer) cells at a rate of 175 ml/min using conventional centrifugation techniques and devices previously used in whole blood processing. However, in the processing of TIL (Tumor Infiltrating Lymphocytes), the volume of cultured cells that must be processed is increased by an order of magnitude to approximately 100 to 400 liters. Conventional blood processing techniques and devices cannot effectively deal with these large fluid volumes and the attendant need to increase the processing rates.
Furthermore, the necessarily high inlet flow rates can lead to confused, turbulent flow conditions within the centrifugation chamber. These flow conditions are not desireable, because they can interfere with sedimentation and separation within the centrifugal force field. Thus, despite the high inlet flow rates, the overall effectiveness and efficiency of the process suffers.
High inlet flow rates and resulting confused, turbulent flow conditions can also result in a non-uniform distribution of the fluid within the centrifugation chamber.
Often, then, it is necessary to reduce the inlet flow rate below the desired amount in the interest of obtaining the flow conditions within the processing chamber conducive to optimal separation.